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The Architect of the Microscopic World: How do cellular connections build the foundation of multicellular organisms?
In the world of multicellular organisms, interactions between cells are not accidental but core to the health and development of organisms. These interactions allow cells to effectively transmit signals and communicate amidst changes in the microenvironment, thereby helping to maintain the normal functions and physiological balance of organisms. Whether it is stable cell connections or transient cell interactions, they play indispensable roles in different physiological processes.
Stable cell interactions
Stable cell-cell interactions are critical for cell adhesion and control of shape and function in tissues. Most of these interactions rely on intercellular junctions, which are complexes of proteins that provide contact between neighboring cells.
Cell junctions not only ensure the integrity of the epithelial cell layer but also assist in tissue organization.
Tight connections
Tight junctions are multi-protein complexes that tightly connect cells of the same tissue and prevent the movement of water and water-soluble molecules between cells. These junctions in epithelial cells also separate the extracellular fluid surrounding their apical and basal membranes. In addition, the permeability of these connections can be affected by factors such as protein composition, tissue type, and cell-to-cell signaling.
Anchor connection
Of the three types of anchoring junctions, only two are involved in cell-cell interactions: adherens junctions and desmosomes. Adherens junctions are found in many types of cells and their function is to give cells and tissues shape and tension. In addition, desmosomes are also a key site for cell-to-cell signaling, providing support for maintaining cell strength and resilience.
Gap junction
Gap junctions are the primary site of signaling between cells, allowing small molecules to diffuse between adjacent cells. In vertebrates, gap junctions are composed of transmembrane proteins called connexins that form hexagonal pores that allow ions, sugars, and other small molecules to pass through.
Instant interaction
Immune system
White blood cells play a vital role in protecting the body from threats from foreign substances. The interactions of these cells are transient but critical for triggering an immune response. When an infection occurs, white blood cells need to move from the blood into the affected tissue, a process called extravasation.
Coagulation process
Coagulation depends on the interaction between platelets in addition to the production of fibrin. In the event of endothelial injury, platelets immediately adhere to the exposed connective tissue and release signals to recruit more platelets to participate.
Interactions between bacteria
The interactions between bacterial populations are similar to those of cells in tissues. They communicate through physical interactions and signaling molecules to regulate each other's metabolism and growth. The formation of biofilm is a good example, which enhances the ability of bacteria to adapt to environmental changes.
Pathological effects
Cancer
Cancer often arises from the loss of cell-cell interactions. Normal cells are restricted from growing when they come into contact with surrounding cells, but cancer cells often lose this mechanism.
Bacterial Pathogens
Pathogenic bacteria require interaction with host cells to invade. These interactions involve strong attachment properties that enable the bacteria to firmly attach to the host cell surface.
Disease
Disturbance of cell-cell interactions may lead to the occurrence of a variety of diseases. For example, autoimmune diseases and abnormal cell function caused by genetic mutations are associated with disruptions in cell-cell interactions.
Cell connections and interactions in the microscopic world shape every aspect of our lives. So, how many unsolved biological secrets are hidden between these small structures and functions?
